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ABSTRACT: Human parainfluenza viruses (hPIV) are pathogens responsible for upper and lower respiratory tract infections. We previously described clinical variant strains of hPIV-2 that display unusual large syncytial cytopathic effects. Their molecular characterization revealed a recurrent conserved specific amino acid substitution: A96T in the F2 subunit of the fusion glycoprotein F. The objective of this study was to investigate the contribution of this A96T substitution to the specific hyperfusogenic properties of the hPIV-2 variant strains. Based on a transient expression strategy, quantification of cell-cell fusion assays, and flow cytometry, we have shown that the A96T mutation strongly alters the fusogenic properties of F hPIV-2, highlighting this key residue in the F2 subunit and its possible role in fusion regulation. This work highlights the benefits of monitoring genetic and phenotypic changes of circulating strains to complete our understanding of Paramyxovirus fusion and related pathogenesis.
Virus Genes 06/2013; · 1.85 Impact Factor
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ABSTRACT: Alternative splicing and post-translational modifications are processes that give rise to the complexity of the proteome. The nuclear ATF7 and ATF2 (activating transcription factor) are structurally homologous leucine zipper transcription factors encoded by distinct genes. Stress and growth factors activate ATF2 and ATF7 mainly via sequential phosphorylation of two conserved threonine residues in their activation domain. Distinct protein kinases, among which mitogen-activated protein kinases (MAPK), phosphorylate ATF2 and ATF7 first on Thr71/Thr53 and next on Thr69/Thr51 residues respectively, resulting in transcriptional activation. Here, we identify and characterize a cytoplasmic alternatively spliced isoform of ATF7. This variant, named ATF7-4, inhibits both ATF2 and ATF7 transcriptional activities by impairing the first phosphorylation event on Thr71/Thr53 residues. ATF7-4 indeed sequesters the Thr53-phosphorylating kinase in the cytoplasm. Upon stimulus-induced phosphorylation, ATF7-4 is poly-ubiquitinated and degraded, enabling the release of the kinase and ATF7/ATF2 activation. Our data therefore conclusively establish that ATF7-4 is an important cytoplasmic negative regulator of ATF7 and ATF2 transcription factors.
PLoS ONE 01/2011; 6(8):e23351. · 4.09 Impact Factor
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ABSTRACT: The product of adenovirus type 5 (Ad5) gene IX, protein IX (pIX), is a multifunctional protein that stabilizes the viral capsid and has transcriptional activity. We show that pIX also contributes to the Ad5-induced reorganization of the host-cell nuclear ultrastructure: pIX induces the formation of specific and dynamic nuclear inclusions, and the host promyelocytic leukaemia (PML) protein, which is the main structural organizer of PML bodies, is stably relocated and confined within the pIX-induced inclusions late in infection. Our results suggest that Ad5 has evolved a unique strategy that leads to the sustained neutralization of PML bodies throughout infection, thereby ensuring optimal viral proliferation.
EMBO Reports 11/2003; 4(10):969-75. · 7.36 Impact Factor
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ABSTRACT: The effects of the adenovirus infection on the distribution of the cellular protein kinase CK2 and double-stranded RNA-activated protein kinase (PKR) were examined at the ultrastructural level. Immunogold labeling revealed the redistribution of CK2 subunits and PKR to morphologically distinct structures of the cell nucleus. The electron-clear amorphous structures, designated pIX nuclear bodies in our previous work (Rosa-Calatrava et al., 2001), contained CK2 alpha and PKR. The protein crystals, which result from the regular assembly of hexon, penton base, and fiber proteins [Boulanger et al. (1970) J Gen Virol 6:329-332], contained CK2 beta and PKR. Both viral structures were devoid of viral RNA, including the PKR-inhibitor VA1 RNA generated by the RNA polymerase III. Instead, VA1 RNA accumulated in PKR-free viral compact rings in which the viral RNA generated by the RNA polymerase II was excluded.
Microscopy Research and Technique 04/2002; 56(6):465-78. · 1.79 Impact Factor
